Dwarf schefflera bonsai

Placement

Heptapleurum arboricola, long known as Schefflera arboricola, is a tropical shrub that can stay indoors all year round. It copes with low light and low humidity, but it grows much better and produces smaller leaves when it gets plenty of light. Place it near a south-, west- or east-facing window, behind a sheer curtain: indoors, strong direct sun burns the leaves.

The ideal temperature is 64 °F to 72 °F, and it should never drop below 50 °F. In winter, if you open windows to air the room, make sure the tree is not hit by cold air. In summer it can go outside to a sheltered spot once temperatures no longer dip below 61 °F.

It appreciates high humidity. To raise the humidity around it, set the pot on a tray of wet pebbles, keeping the water line below the surface of the stones.

Soil mix

A standard bonsai mix suits it. It is not fussy about the ingredients as long as the mix drains well; slightly alkaline conditions suit it. A mineral blend of akadama, pumice and lava rock, sifted to remove dust, drains and aerates the roots well.

Many scheffleras sold at garden centers are planted in an organic potting soil that holds too much water and, once it dries out completely, is hard to rewet: water runs down the side of the pot without soaking the root ball. If yours is like this, repot it into a proper bonsai mix the following spring.

Watering

Dwarf schefflera likes a moist mix that is never allowed to dry out. Water thoroughly as soon as the surface starts to dry, then let the excess drain away: avoid overwatering. Do not water on a fixed schedule; needs change with light, warmth and season. In winter, water more cautiously, unless the tree sits above a heater: the root ball then dries very fast and needs close watching. Leaf drop can signal a mix that is either too wet or too dry.

Fertilizer: from spring to fall, apply liquid fertilizer every week, following the label rate, then once a month in winter. In summer you can also use solid organic fertilizer.

Pruning

Pruning is the main tool for shaping a schefflera. A new shoot always grows from the axil of the leaf just below the cut and points in the same direction as that leaf, so choose where to cut according to the direction you want. If the tree becomes sparse and leggy, cut it back freely.

For finer branching, remove the largest leaves but leave about 0 in of leaf stalk attached to the stem. That stub drops off by itself, pushed away by new growth, and the start of a new twig often appears at that spot. As soon as the new twig has two or three small leaves, cut its tip.

A very healthy tree can be fully defoliated while the tips of the twigs are cut back at the same time: it then pushes lots of new shoots, gains ramification and produces smaller leaves. Dwarf schefflera forms neither hard wood nor rough bark, but steady pruning gradually gives the trunk some taper. It is often grown with a broad crown, in the silhouette of a banyan tree.

Aerial roots add a great deal of character to this bonsai.

Wiring

Wiring is not a very promising technique for this species. Its trunk and branches, which never form hard wood, snap easily when bent too far. Younger shoots are more flexible and can be wired with less risk; some growers even find that careful wiring helps their wood harden faster.

If you do wire, use aluminum wire about a third as thick as the twig, coiled at roughly 45°, and bend very gradually. Check the tree regularly and remove the wire before it marks the bark, cutting it at every turn rather than unwinding it.

Repotting

Repot every other year in spring; a young, vigorous tree can be repotted every year. The fleshy roots break easily, so untangle them very gently. Even so, a tree in top condition tolerates hard root pruning. Replant in a free-draining mix and wait for the tree to recover before any major pruning.

Dwarf schefflera propagates easily from cuttings, which root in potting mix or even in a glass of water, as well as from seed and air layers.

Insects seldom attack it. Indoors, watch for scale, mealybugs and spider mites; against scale, a suitable oil-based insecticide works well. There are no serious diseases to worry about. Finally, all parts of the plant are toxic to dogs and cats, so keep the bonsai out of their reach.